Apple has invited media to a "special event" in its hometown of Cupertino, California, on Sept. 9, when the iPhone maker is expected to unveil the latest versions of its smartphones.

Apple's invitation reads: "Wish we could say more." It came on a black-and-white background dominated by the company's corporate logo.

Apple is expected to unveil larger 4.7-inch and 5.5-inch screens for iPhones. The company may also introduce its long-awaited smartwatch.

Much of the pre-event speculation for the iPhones has centered on the use of "sapphire" display screens said to be more scratch-resistant. For sure, the new devices will incorporate new software features such as HomeKit, which will help manage connected devices within the home, and HealthKit, a central repository of health data and services.

According to an FT report, Apple is also working with NXP Semiconductors NV to add secure near-field communications (NFC) technology into the next iPhone, which would enable the smartphone users to pay by touch, the Financial Times reported, citing people familiar with Apple's plans.

And a patent application by Apple details a wireless charging system that could be used for a smartwatch.

The U.S. Patent & Trademark Office on Thursday published an application filed in early 2013 by Apple for a patent on wireless charging technology that shows how it could be used on a smartwatch or other Apple products.

Apple's patent application says the wireless charging technology could also double as an antenna for near-field communication, a technology that allows a device to easily talk to other NFC-enabled gadgets.